A head-up display generates an augmented reality (AR: Augmented Reality (AR)), which adds information to an actual scene and emphasizes a specific object in an actual scene by displaying an overlapping image on a scene (real view) in front of a vehicle, and contributes to safe and comfortable vehicle operation by accurately providing desired information while minimizing an eye movement of a viewer driving a vehicle.
For example, Patent Literature 1 discloses a head-up display, which comprises two image display units and displays an image on these image display units to thereby generate a virtual image on two imaginary virtual image display surfaces. In the head-up display, display surfaces of first and second image display units are arranged at different angles with respect to a a viewer's line of sight so that two virtual image display surfaces generated by the first and second image display units are recognized at different viewing angles. Specifically, the head-up display generates one virtual image display surface to be substantially vertical to a viewer's line of sight, and the other virtual image display surface to be inclined in a horizontal direction from the one virtual image display surface. That is, two virtual image display surfaces are not parallel, but have a predetermined angle. As two virtual image display surfaces are inclined by a predetermined angle, a viewer can sterically recognize a virtual image displayed on a respective virtual image display surface.